CVE-2026-18663
MEDIUMDescription
A flaw was found in 389-ds-base. The get_ldapmessage_controls_ext() function frees the parsed controls array on the Session Tracking critical-control rejection path without clearing the SLAPI_REQCONTROLS pblock slot. Operation teardown then frees the same pointer again, causing a double-free. An unauthenticated remote attacker can trigger this with a single BIND request carrying a critical Session Tracking control, resulting in heap corruption and potential denial of service.
How to fix
TridentStack Control can deploy fixes like this automatically across your Windows, macOS, and Linux fleet. See how it works
Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.
CVSS v3 Vector
Exploitability
Impact
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
Exploit Intelligence
Low risk: more likely to be exploited than 37% of all known CVEs.
References
Related Vulnerabilities
Other CWE-415 vulnerabilities, ordered by exploit likelihood. View all
| CVE | Severity | CVSS | EPSS | Exploited | Fix |
|---|---|---|---|---|---|
| CVE-2023-25136 | Medium | 6.5 | 90% | - | Fix |
| CVE-2003-0545 | Critical | 9.8 | 87% | - | Fix |
| CVE-2018-0101 | Critical | 10.0 | 87% | - | Fix |
| CVE-2026-33824 | Critical | 9.8 | 73% | KEV | Fix |
| CVE-2019-3829 | Medium | 5.3 | 59% | - | Fix |
| CVE-2021-3407 | Medium | 5.5 | 50% | - | Fix |
Common questions
How do I fix CVE-2026-18663?
Upgrade 389-ds-base on debian unstable to 3.3.1-1 or later.
Is CVE-2026-18663 being actively exploited?
Not that we know of. CVE-2026-18663 is not in the CISA Known Exploited Vulnerabilities catalog. Its EPSS score of 0.43% is the estimated probability that it will be exploited in the next 30 days. That is higher than 37% of all scored CVEs.
How severe is CVE-2026-18663?
CVE-2026-18663 has a CVSS v3 base score of 5.9, rated medium. CVSS rates the technical impact if the vulnerability is exploited, not how likely that is, so weigh it alongside the exploit-prediction score when you decide what to patch first.
What does CVE-2026-18663 affect?
Published advisories record a fix for 389-ds-base (Debian). Only products with a sourced advisory are listed, so treat this as what we can cite rather than a complete inventory.
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Markdown
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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-08-14.